Approximately twelve percent of newborns are born preterm in the U.S. These preterm newborns frequently require long, expensive, and stressful hospital stays in neonatal intensive care units (NICUs), and present a number of unique challenges. Studies have shown that the total brain weight achieved at 34 weeks can be as little as 65% of that of a full term newborn, with the remaining brain development occurring outside the protection of the utero environment. Further studies have shown that preterm newborns exhibit decreased cerebral cortex volume and cerebellar growth when compared to their full term counterparts, frequently emerging from NICUs having developmental and neurosensory deficits.
Advances in preterm newborn developmental research suggest that the loud, atypical acoustic environments characteristic of NICUs may contribute to the decreased cerebral cortex volume and cerebellar growth, resulting in negative outcomes involving hearing, growth, and ultimately, cognition. Exposure of preterm newborns to environmental stimuli that do not correspond to the normal in-utero acoustic environment induces stress, which negatively impacts sleep, growth, and sensory development processes. The negative impact is thought to disrupt and alter normal brain development in response to the external environmental stimuli.
Generally, a mother's body and amniotic fluid surround a developing fetus, providing a natural acoustic filter, with sound attenuation increasing as a function of frequency. The gravid uterus plus amniotic fluid provides negligible sound attenuation of frequencies less than about 300 Hz, then sound attenuation increases monotonically up to 15-20 decibels (dB) at about 2,000 Hz. Above 2,000 Hz, the gravid uterus effectively blocks sound, i.e. attenuation is 15-20 dB or greater.
Attempts have been made to adapt NICUs to reduce the environmental noise levels, including the installation of low-noise incubation equipment and sound-absorbing materials in floors, walls, and ceilings. Other attempts include the use of single-bed NICU rooms to allow better control of the environmental noise levels. While these approaches do reduce some environmental noise, they are only marginally effective, and are often cost prohibitive for many institutions.
Further attempts to reduce environmental noise include the use of foam earcups that are placed over the ears of a preterm newborn, and attached through the use of an adhesive. While the foam earcups do provide limited sound attenuation, the filtered sound profile does not correspond to the normal in-utero acoustic environment. As a result, the effectiveness of the foam earcups is extremely limited.
Another unique challenge with preterm newborns is that their skin and facial features are very delicate and extremely susceptible to damage, such as tearing. This presents several problems for implementation of devices to support development.
Firstly, the foam earcups rely on a hydrogel adhesive to bond the earcup to the skin to form an acoustic seal. The hydrogel adhesive is very sensitive to conditions of application. If the foam ear cup is very lightly positioned, in order to prevent damage to the skin, the adhesive bond is very weak, and the bond between the earcups and the skin of the preterm newborn fails within a few hours. In other instances, the adhesive bond to the skin is too strong, and extreme care must be taken when peeling the bonded earcup away from the skin to remove the foam earcup. Often, the removal process results in damage to the skin, such as tearing or irritation.
Secondly, the underdeveloped lungs in preterm newborns frequently require respiratory support in the form of conventional mechanical ventilation, high frequency ventilation, or continuous positive airway pressure (CPAP) delivered through respiratory support tubes positioned in the oral cavity or nose by a nasal cannula. While there are many conventional respiratory support tube attachment devices available for full-term newborns and adults, these devices are not suited for the delicate skin or nasal septum of preterm newborns. Consequently, the respiratory support tubes are commonly attached to fabric caps by safety pins and rubber bands, or directly to the skin of the preterm newborn by medical tape. Extreme care must be taken during removal of the medical tape, to avoid injury to the preterm newborn.
Consequently, there is a strong need for a medical headgear that is suitable for use on preterm newborns, that reduces environmental noise to in-utero acoustic levels, and provides a stable support for attaching respiratory support tubes and other medical devices.